1. Field of the Invention
This invention relates to a storage system comprising a plurality of different types of storage subsystems with different processing performance.
2. Description of the Related Art
A storage system is configured with for example disk drives arranged in an array, and provides a storage area based on a RAID (Redundant Array of Independent Inexpensive Disks). A logical volume (logical device), which is a logical storage area, is formed in the physical storage areas of each disk drive. A host computer (server) can read and write the desired data by issuing a write command or read command in a prescribed format to the storage system.
However, the performance of disk drives continues to improve each year, and storage subsystems are used over extended periods of time. Hence there are cases in which high-speed disk drives and low-speed disk drives coexist within the same storage subsystem. Consequently in order to make effective use of disk drives, so-called data migration techniques, in which frequently-used data is moved to high-speed disk drives and infrequently-used data is moved to low-speed disk drives, have been proposed (Japanese Patent Laid-open No. 2003-216460).
In the technology of the prior art, high-speed disk drives and low-speed disk drives are intermixed in the same storage system, and data is relocated according to frequency of data use. However, in conventional technology data cannot be relocated spanning different types of storage subsystems. Moreover, in conventional technology it is possible to copy the contents of volumes spanning storage subsystems, but this is merely performed for purposes of so-called disaster recovery, and optimal location of volumes according to the state of use of each storage subsystem is not possible.
With advances in computer and network technology, there have been steady improvements in the performance of storage subsystems. Further, the quantity of data to be managed by enterprises, municipalities, schools and other organizations increases each year, and while there is always a desire for storage systems with enhanced performance, storage subsystems are expensive system products.
Hence systems may be constructed in which, for example, while an old-type storage system continues operation a higher-performance storage system is newly introduced, and the new and old storage systems are operated in concert. And, storage systems may be constructed in which mid-scale storage subsystems are positioned in different departments, with a large-scale storage subsystem installed in a computer room linked with mid-scale storage subsystems.
In this way, there are cases in which storage subsystems with different processing performance are connected and operated together. However, conventional technology does not take into consideration the relocation of volumes in an environment in which different storage subsystems coexist, so that automatic relocation of volumes according to the state of use is not possible even when there is uneven use among storage subsystems; consequently such systems cannot be used efficiently.
For example, after the initial construction of a system, there are cases in which the frequency of use of a storage subsystem with relatively poor performance is greater than the frequency of use of a high-performance storage subsystem. And, there are cases in which the frequency of use of a volume placed in a high-performance storage subsystem declines, so that the storage resources of the high-performance storage subsystem are wasted.
Thus when unevenness in the use of storage subsystems occurs in a heterogeneous environment in which different types of storage subsystems coexist, a system administrator studies the relocation of volumes. When relocating volumes, the system administrator must perform volume copying of a volume to be moved to another storage subsystem, cause the relocated volume to be recognized again by the server, and confirm operation. Hence the tasks involved are complex, and the storage system is difficult to use.